How to Alum Paper for Marbling

Marbling paper in the Ebru (Turkish) style of marbling requires that the paper first be treated using a mordant, in this case an alum mixture. The alum helps the pigments used in marbling to adhere to the paper. Without a mordant the pigments will slide off the paper.

Alum, or Potassium Aluminum Sulfate, is a chemical often used as a food preservative. It is sold in a dry crystal form, and is soluble in water.

When aluming paper it’s important to first mark the back of your sheets. This is critical as it’s nearly impossible to identify which side has been alummed after the sheet has dried. If you marble on the wrong side, the pigments will not properly adhere to the paper.

A touch of hot water helps to liquify the alum and ensure that it is entirely dissolved.

Tip: When mixing the alum it’s helpful to jumpstart the melting process by first using a bit of hot water.

This helps to liquify the alum and ensures that it has been properly and entirely dissolved. Fill the remainder of the container with cold tap water.

It’s also important to wear a dust mask as airborne alum should not be inhaled.

There are two different ways to apply alum to the paper.

Place paper in bath holding opposing corners to help eliminate air bubbles.

The first we will call the “quick method.” This method works great for larger quantities of paper requires that the alum mixture be poured into your marbling tray. Wear gloves: while alum is not toxic, it will dry out your skin.
Hold paper by opposing corners and gently lay it down in the bath. Do your best to avoid trapping any air bubbles beneath the sheet. Air bubbles that are trapped under the surface will result in an uncoated section where the pigments will not stick when marbling.

Drain your sheet, and then let it dry on a drying rack. Once dry the sheets can be placed in a press to flatten. If they are still wrinkly, an iron can be used at a low setting to flatten the sheets. Still not working? Lightly spray the sheets with water and then iron.

Drain paper into bath before drying.

As an alternative method to drying and flattening, you can place two sheets of alumed paper, with their alumed sides facing each other and sandwich them between sheets of blotting paper. Each bundle is then interleaved with sheets of cardboard and left to dry. This method will reduce the number of wrinkles and produce a flatter sheet.

Use a sponge to apply alum moving from the center of the sheet out.

The second method for aluming paper is using a sponge or a brush. Simply dip the sponge in the alum mixture and apply to the paper moving from the center of the sheet out. This technique is used to help reduce the number of wrinkles. Make sure that you do not miss any spots, as uncovered areas will not hold pigments during the actual marbling process.

Now you’re paper is ready to marble!

Remember, alummed paper has a shelf life and it’s best to use within 4 days or preparing.